最大冻结深度是季节冻土的重要指标，预测第三极地区未来最大冻结深度的变化，对于理解该区域的环境变化，指导生态保护、农牧业生产、工程建设等都具有重要意义。本研究利用基准时期（2000s）良好训练的支持向量回归模型，使用集合模拟策略，预测了2050s和2090s第三极地区在4种SSP情景下最大冻结深度的变化。结果表明，在可持续路径（SSP126）、中间路径（SSP245）、区域竞争路径（SSP370）和化石燃料为主发展路径（SSP585）情景下，不包括多年冻土退化为季节冻土的区域，相对于基准期，季节冻土的最大冻结深度到21世纪末将分别减小10.41 cm（11.69%）、24.00 cm（26.95%）、37.71 cm（42.34%）和47.71 cm（53.57%）。最大冻结深度的减小具有海拔依赖性，随着海拔的升高，最大冻结深度减小的速率变大，但是海拔超过5 000 m后，最大冻结深度减小速率逐渐减小，这与升温的海拔依赖性较为一致。最大冻结深度的变化也与生物群区有关，在4种SSP情景下，山地草地和灌木区的最大冻结深度减小速率最快，到21世纪末平均每十年分别减小1.80 cm、3.77 cm、5.77 cm和7.24 cm。分流域来看，青海湖流域减小速率最快。模拟预测结果可通过国家青藏高原科学数据中心（DOI：10.11888/Cryos.tpdc.273002）下载使用。该研究结果可为在全球变暖背景下理解第三极季节冻土的未来变化及其生态水文效应提供基础数据与信息。

The maximum frost depth （MFD） is an important indicator for seasonally frozen ground. The forecasting of future changes in the MFD is important for understanding environmental changes， ecological protection， agricultural and livestock production， and engineering construction in the Third Pole. However， future changes in the MFD of seasonally frozen ground in the Third Pole have not been report yet. In this study， an ensemble simulation strategy （i.e.， the model is run 200 times， and the arithmetic mean of 200 times is used as the final simulation result） is used to simulate the MFD for the 2050s and 2090s under four SSP scenarios， i.e.， green scenario （SSP126）， historical scenario （SSP245）， weak mitigation scenario （SSP370） and rapid and unconstrained growth scenario （SSP585） using a well-trained support vector regression model for the baseline period （2001—2010）. The spatial and temporal characteristics of the MFD in the seasonally frozen ground area from the baseline period to 2050s and 2090s are analyzed. In addition， the characteristics of the MFD change in different elevations and biomes （mountain grasslands and shrubs， temperate grasslands and shrubs， desert and dry shrubs， and temperate coniferous forests） are analyzed. The results indicated that the future MFD in the Third Pole would continue to decrease by 10.41 cm， 24.00 cm， 37.71 cm， and 47.71 cm， respectively， from 2001 to 2100 under the SSP126， SSP24， SSP370， and SSP585 scenarios， excluding the degradation of permafrost to seasonally frozen ground. The change of MFD was elevation-dependent and related to biomes. The decrease rate of MFD increased with the increase of elevation， but the decrease rate of MFD gradually decreased after the elevation exceeded 5 000 m， which is consistent with the elevation dependence of warming. Under the four SSP scenarios， the decrease rate of MFD is highest in the mountain grassland and shrub area， with an average decrease of 1.80 cm， 3.77 cm， 5.77 cm， and 7.24 cm per decade， respectively， by the end of the century. Among the 21 basins related to the Third Pole， the largest MFD reduction occurred in the Qinghai Lake basin. The future MFD dataset in 2050s and 2090s can be free downloaded through the National Tibetan Plateau Data Center （DOI：10.11888/Cryos.tpdc.273002）. The results provide basic data and information for understanding the future seasonally frozen ground change in the Third Pole and its ecological and hydrological effects in the context of global warming.